When the white dwarf has accreted more then 1.4M electron degenracy pressure cannot stop gravitational collapse. The white dwarf will collapse, heat enormously fast and ignite a runaway chain of fusion reactions. This sudden release of energy will destroy the entire star in the most impressive of explosions seen in the entire Universe, a Supernova. This situation is called Supernova type Ia. The explosion completely disrupts the white dwarf and even the companion if it is too close. The explosion is so luminous that it can outshine an entire galaxy for several days and be seen across the vast expanses of the Universe. During the explosion there are numerous complex fusion reactions that take place. They can fuse many of the natural elements found on Earth. The material is sent back into the ISM to mix. The Supernova sends out an enormous shock wave that expands for hundreds of thousands of years. It smashes into the ISM and can create perturbations that will cause gravitational collapse and new star formation. In this star's final blaze of glory it seeds the Universe for the next generation!